The expulsion of hydrocarbon vapor during the act of refueling a motor vehicle has long been a pressing concern in the motor vehicle industry. During the past 20 years the United States Government, through the Environmental Protection Agency, and the various states have proposed increasingly stringent regulations designed to decrease the evaporative emission of hydrocarbons to the atmosphere. State and federal regulations, effective in 1991, require that all motor vehicles provide an onboard method of capturing hydrocarbon vapor displaced from an automobile fuel tank during the refueling process. The captured vapor must be stored on the vehicle for consumption by the engine as the vehicle is operated. The regulations further require that no hydrocarbon vapor be released to the atmosphere when the fuel cap is removed from the fill neck and the fuel nozzle is inserted into the fill neck during the act of refueling a vehicle.
Over the years, the motor vehicle industry has designed a variety of valves and vent systems which address some of the individual requirements for environmentally safe operation, such as improved fuel filler caps, rollover valves, and the like. The present invention provides a distinct improvement over these individual components by providing a comprehensive refueling vapor recovery system which allows fueling against a predetermined tank pressure and which vents all refueling vapor to a storage canister through an appropriate flow valve mounted in the vapor dome of the fuel tank. The present invention provides for the venting of all evaporative emissions and refueling vapor through the same valve and is in continuous use whether the motor vehicle is operative or being refueled.